Method for expanding cd4+cd25+t regulator cells

ABSTRACT

A method for generating/expanding in vitro a CD4 + CD25 +  T regulatory (Tr) cell and the use thereof in the treatment of diseases associated with a cell-mediated immune response (including T- and antibody-mediated responses).

FIELD OF THE INVENTION

The present invention relates to methods for generating/expanding invitro a CD4⁺CD25⁺ T regulatory (Tr) cell or population and the use ofsuch a cell or population for the treatment of diseases associated witha cell-mediated immune response (including T- and antibody-mediatedimmune responses). The present invention also relates to methods ofeliminating/reducing a CD4⁺CD25⁻ T effector cell or a populationthereof.

BACKGROUND OF THE INVENTION

The modulation of cell-mediated immune responses (including T- andantibody-mediated immune responses) is important in a therapeuticcontext.

Organ and cell transplantation is the treatment of choice for mostpatients with end stage kidney-failure, heart or liver disease,autoimmune type 1 diabetes and it is a developing possibility forpatients with deficiencies in small-bowel function. Graft survivaldepends on a number of factors but the most significant of these is theadministration of powerful immunosuppressive drugs. Transplantationbetween genetically disparate individuals evokes a rapid and potentiallydestructive alloreactive immune response that, if left uncontrolled, canlead to complete destruction of the transplanted organ or to graftversus host disease (GVHD). Administration of immunosuppressive drugsattenuates this response and thus prevents acute graft rejection.However, continued graft survival depends on life-long or prolongedimmunosuppression because withdrawal of immunosuppression results inre-activation of the rejection response, leading to rapid graftdestruction.

Although the currently available immunosuppressive drugs are veryeffective in short term, substantial problems indicate a pressing needto develop alternative and more sophisticated ways of preventing graftrejection. The main obstacle is the inability to distinguish betweenbeneficial immune responses against infectious pathogens and destructiveimmune responses against the graft. Thus, immunosuppressive therapiescan lead to increased risk of opportunistic infections. Several studiesshow that non-specific immunosuppression would lead to an increasedincidence of cancer in transplanted patients (Hojo 1999). Therefore, thefull potential of transplantation will be realised only whenalternatives to non-specific immunosuppression will be found. The majoraim of transplantation immunology is to develop protocols that preventimmune responses towards the graft but leave the rest of the immunesystem intact. This accomplishment will lead to transplantationtolerance.

In autoimmune diseases, undesired immune responses to self-antigens leadto destruction of peripheral tissues. Treatments of autoimmune diseasesare currently based on down-modulation of inflammation and non-antigen(Ag) specific immunosuppression. As for prevention of allograftrejection, this strategy is frequently not effective in the long termwith high risk of relapse once the drug is withdrawn and hazards ofexcessive immunosuppression, including infections and tumors. Thealternative approach is based on the induction of transientimmunosuppression and/or specific immune tolerance, aimed at “silencing”the pathogenic response to self-Ag, while keeping host defensemechanisms intact.

The immune system has evolved two distinct mechanisms to inducetolerance to self or non-harmful antigens. These are referred to ascentral and peripheral T cell tolerance. Central tolerance is realizedduring fetal development and the very early natal period and is mediatedby clonal deletion of self-reactive T cells during thymic development.Peripheral mechanisms induce tolerance in mature T cells and occur inthe periphery during the whole life. These mechanisms include functionalinactivation of antigen specific lymphocytes (named anergy) andactivation of T cell subsets with suppressive and regulatory capacities(reviewed in Battaglia 2002).

Recently, there has been a growing interest in the induction of Tregulatory (Tr) cells as a strategy to achieve immunological tolerance.The majority of Tr cells identified to date lie within the CD4⁺population, and the CD4⁺ Tr cells that constitutively express the IL-2Rαchain (CD25) are one of the best characterized so far both in mouse andhumans. Our invention concentrates on this Tr cell subset identified asCD4⁺CD25⁺ Tr cells.

SUMMARY OF THE INVENTION

Rapamycin is an immunosuppressive compound that, by binding themammalian target of rapamycin (mTOR), inhibits cytokines induced T-cellproliferation (Sehgal 1998). Rapamycin is currently used to preventacute graft rejection in humans, and has been shown to allow operationaltolerance in murine models of transplantation (Blaha 2003). However, adirect effect of rapamycin on Tr cells, which play a key role in theinduction and maintenance of peripheral tolerance, has not beendemonstrated so far. We have now found that rapamycin selectivelyexpands or promotes the naturally occurring CD4⁺CD25⁺ Tr cells in vitro.Thus, rapamycin can be used to generate/expand CD4⁺CD25⁺ Tr cells forex-vivo cellular therapy in T cell-mediated diseases.

We have found that in vitro treatment of CD4⁺ T cells, which includesboth CD4⁺CD25⁺ Tr cells (5-10% of the total CD4⁺ T cells) and T effectorcells, with rapamycin increases by 20 fold the CD4⁺CD25⁺ Tr cellcontent.

The ability of rapamycin to selectively expand CD4⁺CD25⁺ Tr cells insuch large amounts may be limited to the in vitro approach.

We have also found that rapamycin in vitro selectively eliminatesCD4⁺CD25⁻ T effector cells from a population of T cells comprising bothsuch T effector cells and CD4⁺CD25⁺ Tr cells.

STATEMENTS OF THE INVENTION

According to one aspect of the present invention there is provided amethod for producing, including culturing, a CD4⁺CD25⁺ T regulatory (Tr)cell comprising incubating a T cell or T cell population obtained from ahuman or animal with rapamycin or a derivative thereof.

According to another aspect of the present invention there is provided amethod for generating or expanding the population of CD4⁺CD25⁺ Tr cellsin a population of T cells comprising incubating the population of Tcell obtained from a human or animal with rapamycin or a derivativethereof.

Thus, we have found that rapamycin or a derivative thereof allows theculturing of, promotes expansion or proliferation of functionalCD4⁺CD25⁺ Tr cells and in particular CD4⁺CD25⁺FOXP3⁺ Tr cells.

By “functional CD4⁺CD25⁺ Tr cells”, we mean that the CD4⁺CD25⁺ Tr cellsretain their suppressive activity and/or that the CD4⁺CD25⁺ Tr cellsmaintain expression of regulatory markers such as FOXP3.

According to another aspect of the present invention, there is provideda method for selectively eliminating or reducing the number of CD4⁺CD25⁻T cells in a population of T cells comprising incubating the populationof T cells obtainable from a human or animal with rapamycin or aderivative thereof.

In other words, rapamycin selectively blocks T cell receptor—(TCR)mediated proliferation of CD4⁺CD25⁻ T cells, but not of CD4⁺CD25⁺ Trcells.

Whilst not wishing to be bound by any theory it is believed thatCD4⁺CD25⁺ Tr cells may undergo less apoptosis that CD4⁺CD25⁻ T effectorcells in the presence of rapamycin. Alternatively or in addition,rapamycin may block the sensitivity of the T effector cells to IL-2, sothat they do not expand.

It is believed that tumor cell-based therapies such as vaccines and bonemarrow transplants can induce potent, tumor-specific immune diseaserelapse, the most significant post-transplant complication. Unlike thepatient's T cells, which are often functionally impaired by the canceror its treatment, donor T cells are fully functional and are more likelyto mount significant response to the therapy. The present invention maybe advantageous since culturing with rapamycin reduces risks associatedwith T effector cells when T cells are donated to a patient.

In one embodiment, the CD4⁺CD25⁺ Tr cell produced according to thepresent invention is (re-) introduced into a patient alone or incombination with a drug.

In one embodiment the T cell is a naïve T cell.

Preferably the T cell is activated.

In one embodiment the method further comprises incubating in thepresence of a cytokine. Preferably the cytokine is IL-2.

In one embodiment the method further comprises incubating in thepresence of antigens, including allergens, allo-antigens, self-antigens,food antigens, and microbial antigens.

According to another aspect of the present invention there is provided aCD4⁺CD25⁺ Tr cell produced by the method of the invention.

According to another aspect of the present invention there is provideduse of a CD4⁺CD25⁺ Tr cell according to the present invention for themodulation of a cell-mediated immune response.

According to yet another aspect of the present invention there isprovided a pharmaceutical composition comprising the CD4⁺CD25⁺ Tr cellaccording to the present invention and a pharmaceutically acceptablecarrier, excipient or diluent.

According to a further aspect of the present invention there is provideduse of a CD4⁺CD25⁺ Tr cell according to the invention for thepreparation of a medicament for the treatment of a disease associatedwith a cell-mediated immune response.

In previous experiments with type I diabetes, it was reported that Tregulatory cells did not give rise to immune suppression. However,surprisingly therefore we have found that cell-based treatment can beeffective using the method of the present invention. It may be that theprevious experiments did not give rise to immune suppression due to thepresence of T effector cells, which are eliminated using the presentinvention.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1A-1D shows the results of Example 1. FIG. 1A depicts analysis ofcells by FACs. FIG. 1B depicts measurements of CD4+ T cell expansion.FIG. 1C depicts CFSE dilution after 3 rounds of stimulation with APC+OVA(medium) or APC+OVA+rapamycin (rapamycin). FIG. 1D depicts analysis ofcells size by FACS by plotting FSC vs SSC parameters. Small (continuousline) and big (dotted line) cells are circled.

FIGS. 2-7 show the results of Example 2. FIGS. 2A and 2B depict that Tcells activated in the presence of rapamycin were highly enriched inCD4+CD25^(bright) T cells, which represent the Tr subset among theCD4⁺CD25⁺ T cell population. FIG. 2C depicts results of measuring thetotal number of CD4⁺CD25^(bright) T cells by FACS after 3 rounds ofstimulation. FIGS. 3A, 3B, and 4A are plots depicting cell analysis.FIG. 4B summarizes measurement of relative FoxP3 mRNA normalized tocontrol for indicated cell types and treatments. FIGS. 5A and 5C depictcell analysis. FIG. 5B depicts measurements of CD4⁺CD25⁺ T cellexpansion. FIG. 6A depicts cell analysis. FIG. 6B summarizes measurementof relative FoxP3 mRNA normalized to control for indicated cell typesand treatments. FIG. 7 is a graph depicting survival oftransplant-receiving mice over time.

FIGS. 8-10 show the results of Example 3. FIGS. 8 and 10 depict analysisof cells stimulated under specified conditions. FIG. 9 is a graphdepicting diabetes development in experimental mice over time.

FIGS. 11A, 11C, and 11D depict analysis of cells according to Example 4.FIG. 11B depicts the number of CD4⁺ T cells present at the beginning(start) and at the end (4^(th) week) of the culture in the presence orabsence of rapamycin. Each line represents one experiment (n=14).

FIG. 12A-12C depict analysis of cells according to Example 5. FIG. 12Ddepicts the percentage of suppression in each performed experiment.

FIG. 13 depicts analysis of cells according to Example 6.

FIG. 14 depicts analysis of cells according to Example 7.

FIG. 15A depicts analysis of cells according to Example 8. FIG. 15Bdepicts percentages of suppression in comparison to proliferation ofresponder cells.

DETAILED DESCRIPTION OF THE INVENTION

Various preferred features and embodiments of the present invention willnow be described by way of non-limiting example.

Although in general the techniques mentioned herein are well known inthe art, reference may be made in particular to Sambrook et al.,Molecular Cloning, A Laboratory Manual (1989) and Ausubel et al., ShortProtocols in Molecular Biology (1999) 4^(th) Ed, John Wiley & Sons, Inc(as well as the complete version Current Protocols in MolecularBiology).

Rapamycin, a macrolide antibiotic produced by Streptomyceshygroscopicus, is a new effective drug used to prevent allograftrejection (Kahan 2001). Similarly to the immunosuppressants FK506 andcyclosporin A (CsA), rapamycin exerts its effect by binding to theintracellular immunophilin FK506 binding protein (FKBP12). However,unlike FK506 and CsA, rapamycin does not inhibit TCR-induced calcineurinactivity. Rather, the rapamycin-FKBP12 complex inhibits theserine/threonine protein kinase called mTOR (mammalian target ofrapamycin), which activation is required for protein synthesis and cellcycle progression. Therefore, rapamycin blocks signaling in response tocytokines/growth factors, whereas FK506 and CsA exert their inhibitoryeffects by blocking TCR-induced activation (reviewed in Abraham 1996). Adirect effect of rapamycin on Tr has not been demonstrated so far.

This invention provides an ex vivo method of treating or preventingcell-mediated diseases in a mammal in need thereof, which comprises theuse of a rapamycin. As defined herein, the term “a rapamycin” defines aclass of immunosuppressive compounds which contain the basic rapamycinnucleus (shown below). The rapamycins of this invention includecompounds which may be chemically or biologically modified asderivatives of the rapamycin nucleus, while still retainingimmunosuppressive properties.

Accordingly, the term “a rapamycin” includes esters, ethers, oximes,hydrazones, and hydroxylamines of rapamycin, as well as rapamycins inwhich functional groups on the rapamycin nucleus have been modified, forexample through reduction or oxidation. The term “a rapamycin” alsoincludes pharmaceutically acceptable salts of rapamycins, which arecapable of forming such salts, either by virtue of containing an acidicor basic moiety.

It is preferred that the esters and ethers of rapamycin are of thehydroxyl groups at the 42- and/or 31-positions of the rapamycin nucleus,esters and ethers of a hydroxyl group at the 27-position (followingchemical reduction of the 27-ketone), and that the oximes, hydrazones,and hydroxylamines are of a ketone at the 42 position (followingoxidation of the 42-hydroxyl group) and of 27-ketone of the rapamycinnucleus.

Preferred 42- and/or 31-esters and ethers of rapamycin are disclosed inthe following patents, which are all hereby incorporated by reference:alkyl esters (U.S. Pat. No. 4,316,885); aminoalkyl esters (U.S. Pat. No.4,650,803); fluorinated esters (U.S. Pat. No. 5,100,883); amide esters(U.S. Pat. No. 5,118,677); carbamate esters (U.S. Pat. No. 5,118,678);silyl ethers (U.S. Pat. No. 5,120,842); aminoesters (U.S. Pat. No.5,130,307); acetals (U.S. Pat. No. 5,51,413); aminodiesters (U.S. Pat.No. 5,162,333); sulfonate and sulfate esters (U.S. Pat. No. 5,177,203);esters (U.S. Pat. No. 5,221,670); alkoxyesters (U.S. Pat. No.5,233,036); O-aryl, -alkyl, -alkenyl, and -alkynyl ethers (U.S. Pat. No.5,258,389); carbonate esters (U.S. Pat. No. 5,260,300); arylcarbonyl andalkoxycarbonyl carbamates (U.S. Pat. No. 5,262,423); carbamate (U.S.Pat. No. 5,302,584); hydroxyesters (U.S. Pat. No. 5,362,718); hinderedesters (U.S. Pat. No. 5,385,908); heterocyclic esters (U.S. Pat. No.5,385,909); gem-disubstituted esters (U.S. Pat. No. 5,385,910); aminoalkanoic esters (U.S. Pat. No. 5,389,639); phosphorylcarbamate esters(U.S. Pat. No. 5,391,730); carbamate esters (U.S. Pat. No. 5,411,967);carbamate esters (U.S. Pat. No. 5,434,260); amidino carbamate esters(U.S. Pat. No. 5,463,048); carbamate esters (U.S. Pat. No. 5,480,988);carbamate esters (U.S. Pat. No. 5,480,989); carbamate esters (U.S. Pat.No. 5,489,680); hindered N-oxide esters (U.S. Pat. No. 5,491,231);biotin esters (U.S. Pat. No. 5,504,091); O-alkyl ethers (U.S. Pat. No.5,665,772); and PEG esters of rapamycin (U.S. Pat. No. 5,780,462). Thepreparation of these esters and ethers is disclosed in the patentslisted above.

Accordingly examples of rapamycin compounds include compounds offormula:

Wherein RA and RB are each selected from hydrogen and ester or etherforming groups as disclosed in any one of the abovementioned US patents.

Preferred 27-esters and ethers of rapamycin are disclosed in U.S. Pat.No. 5,256,790, which is hereby incorporated by reference. Thepreparation of these esters and ethers is disclosed in theaforementioned patent.

Preferred oximes, hydrazones, and hydroxylamines of rapamycin aredisclosed in U.S. Pat. Nos. 5,373,014, 5,378,836, 5,023,264, and5,563,145, which are hereby incorporated by reference. The preparationof these oximes, hydrazones, and hydroxylamines are disclosed in theabove listed patents. The preparation of 42 oxorapamycin is disclosed in5,023,263, which is hereby incorporated by reference.

Particularly preferred rapamycins include rapamycin [U.S. Pat. No.3,929,992], rapamycin 42-ester with3-hydroxy-2-(hydroxymethyl)-2-methylpropionic acid [U.S. Pat. No.5,362,718], and 42-0-(2-hydroxy) ethyl rapamycin [U.S. Pat. No.5,665,772].

When applicable, pharmaceutically acceptable salts can be formed fromorganic and inorganic acids, for example, acetic, propionic, lactic,citric, tartaric, succinic, fumaric, maleic, malonic, mandelic, malic,phthalic, hydrochloric, hydrobromic, phosphoric, nitric, sulfuric,methanesulfonic, napthalenesulfonic, benzenesulfonic, toluenesulfonic,camphorsulfonic, and similarly known acceptable aids when the rapamycincontains a suitable basic moiety. Salts may also be formed from organicand inorganic bases, such as alkali metal salts (for example, sodium,lithium, or potassium) alkaline earth metal salts, ammonium salts,alkylammonium salts containing 1-6 carbon atoms or dialkylammonium saltscontaining 1-6 carbon atoms in each alkyl group, and trialkylammoniumsalts containing 1-6 carbon atoms in each alkyl group, when therapamycin contains a suitable acidic moiety.

T Regulatory (Tr) Cells

Tr cells are well characterized T cell subsets, which play a key role ininducing and maintaining immunological tolerance. Among the CD4⁺ Trcells, the Tr cell subset that express the IL-2Rα chain (CD4⁺CD25⁺) isone of the most extensively characterized so far (reviewed in Fehervari2004). CD4⁺CD25⁺ Tr cells are generated in the thymus and are part ofthe normal peripheral T cell repertoire. Suppressive CD4⁺CD25⁺ Tr cellscan be distinguished from activated T cells based on the highconstitutive expression of CD25, CTLA-4, GITR, and the transcriptionfactor FOXP3. Once generated, thymic CD4⁺CD25⁺ Tr cells migrate toperipheral tissues, where they potently suppress proliferation andcytokine production by both CD4⁺ and CD8⁺ T cells via a mechanism thatrequires cell-cell contact (Fehervari 2004). CD4⁺CD25⁺ Tr cellscontribute to tolerance induction after solid organ transplantation andprotect from graft versus host disease (GVHD) lethality in bone marrowtransplantion models (Taams 2003). Moreover, it has been demonstratedthat CD4⁺CD25⁺ Tr cells play important immunomodulatory roles in severalanimal models of autoimmunity, allergy, and infection (Fehervari 2004).

Here we provide evidence that in vitro exposure of CD4⁺ T cells torapamycin induces expansion of the naturally occurring CD4⁺CD25⁺FOXP3⁺Tr cells, which retain their suppressive functions in vitro and in vivo.

Preparation of Primed T Cells In Vitro

A population of T cells for use in the present invention may be obtainedfrom peripheral blood or secondary lymphoid organs. The T cells may alsobe obtained from a sample using α-CD4⁺ monoclonal antibody-coatedmicrobeads. In one embodiment the T cells are further purified usingα-CD25⁺ monoclonal antibody-coated microbeads. The T cells may also beobtained from a sample using flow cytometry (FACS). T cells may becultured in a suitable culture medium such as X-VIVO, optionally in thepresence of human serum. Cytokines, such as IL2, may be added.Polyclonal activation of T cells may be induced with α-CD3 and α-CD28antibodies. Alternatively or in addition, an antigen or allergen ofinterest may be added. The T cells are generally co-cultured withantigen presenting cells (APCs). However, it may be preferred to prepareprimed APCs first and then incubate them with T cells. The rapamycin isthen typically added to the culture. The allergen or antigen may beadded before, after or at substantially the same time as the rapamycin.

In one embodiment, the T cells are incubated with rapamycin over aperiod of around 1-4 weeks, preferably around three weeks. Rapamycin maybe added to the medium over the period of this incubation, e.g., once aweek. As an example, rapamycin may be added in an amount of around 100nM.

Therapeutic Uses

The present invention may be used in association with organtransplantation, such as kidney, heart, liver, islet or bone marrowtransplantation, and in the treatment or prevention of graft-versus-hostdisease. For example, in bone marrow allogeneic transplant it has beendemonstrated that ex vivo expanded alloantigen specific CD4⁺CD25⁺ Trcells control graft versus host disease (GVHD), while allowreconstitution of the immune system post-transplantation (Taylor 2002,Trenado 2003, Edinger 2003). CD4⁺CD25⁺ Tr cells may also be able tomodulate GVHD whilst preserving the graft versus tumor (GVT) or graftversus leukemia (GVL) effect.

In more detail, minor histocompatibility antigens (mHags) areimmunogenic peptides from polymorphic cellular proteins that inducestrong T-cell responses after human leukocyte antigen (HLA)-matched,mHag-mismatched stem-cell transplantationmHags with broad or limitedtissue expression are target antigens for graft versus host (GVH) andgraft versus leukemia (GVL) reactivities-Separation of these activitiesis crucial for adoptive immunotherapy of leukemia without GVH disease.

Recent data suggest that patients with autoimmune diseases, such asdiabetes, multiple sclerosis, and rheumatoid arthritis might havedefective or reduced number of CD4⁺CD25⁺ Tr cells. Thus, ex vivocellular therapy to increase the Tr cell compartment is highlyencouraged.

Particular conditions associated with autoimmune diseases which may betreated, include: autoimmune (Hasimoto's) thyroiditis, hyperthyroidism(Graves' disease) type I diabetes mellitus, insulin resistant diabetes,autoimmune adrenal insufficiency (addison's disease), autoimmuneoophoirits, autoimmune orchitis, autoimmune hemolytic anemia, paroxysmalcold hemoglobinuria, autoimmune thrombocytopenia, autoimmuneneutropenia, pernicius anemia, pure red cell anemia, autoimmunecoagulopathies, myasthenia gravis, autoimmune polyneuritis, multiplesclerosis, experimental allergic encephalomyelitis, pemphigus and otherbullous diseases, rheumatic carditis, Goodpasture's syndrome,postcardiotomy syndrome, systemic lupus erythematosus, rheumatoidarthritis, Sjorgen's syndrome, polymyositis, dermatomyositis,scleroderma; inflammatory bowel diseases: Chron's disease, ulcerativecolitis; chronic obstructive pulmonary diseases; chronic inflammatorydiseases; allergic diseases: asthma, atopic dermatitis; fibroticdiseases; and immune reactions to gene therapy derived products.

The present invention also envisages manipulating the expanded cells,for example through cytokine stimulation or by adding genes orinterest—such as therapeutic genes or knock-out genes, prior toadministration to a patient.

As the present invention provides a method for expanding the CD4+CD25+ Tcells it provides a useful tool for readily investigating their functionand cell surface markers. Thus, the present invention further envisagesthe use of the expanded cells in assays.

Administration

The present invention provides a method of using expanded Tr cells incellular therapy. Tr cells from a patient could be isolated and expandedin vitro, and then re-administered to the patient. In anotherembodiment, Tr cells could be obtained from a donor. Preferably thecells are reinfused into the patient.

Tr cells of the present invention for use in immunotherapy are typicallyformulated for administration to patients with a pharmaceuticallyacceptable carrier or diluent to produce a pharmaceutical composition.Suitable carriers and diluents include isotonic saline solutions, forexample phosphate-buffered saline. The composition may be formulated forparenteral, intramuscular, intravenous, intra-peritoneal, injection,intranasal inhalation, lung inhalation, intradermal, intra-articular,intrathecal, or via the alimentary tract (for example, via the Peyerspatches).

Cells and pharmaceutical comprising cells of the invention are typicallyadministered to the patient by intramuscular, intraperitoneal orintravenous injection, or by direct injection into the lymph nodes ofthe patient, preferably by direct injection into the lymph nodes.

Typically from 10⁴/kg to 10⁹/kg treated cells, preferably from 10⁵/kg to10⁷/kg cells, more preferably about 10⁶/kg cells are administered to thepatient.

The routes of administration and dosages described are intended only asa guide since a skilled practitioner will be able to determine readilythe optimum route of administration and dosage for any particularpatient depending on, for example, the age, weight and condition of thepatient.

DESCRIPTION OF THE FIGURES

FIG. 1 shows the results of Example 1.

FIGS. 2-7 show the results of Example 2.

FIGS. 8-10 show the results of Example 3.

FIG. 11 shows the results of Example 4.

FIG. 12 shows the results of Example 5.

FIG. 13 shows the results of Example 6.

FIG. 14 shows the results of Example 7.

FIG. 15 shows the results of Example 8.

EXAMPLES Material and Methods for Examples 1 and 2 Mice.

Balb/c, C57BL/6, and DO11.10 (TCR tg specific for OVA) female mice werepurchased from Charles River Laboratories (Calco, Italy). All mice werekept under specific pathogen free conditions.

Flow Cytometry and Cell Sorting.

Cells were stained with the indicated Abs (all from BD Biosciences,Mountain View, Calif.), and were analyzed with a FACScan flow cytometerequipped with CellQuest software (BD Biosciences). To obtain highlypurified CD4⁺CD25^(+/−) T cells, CD4⁺ T cells were first purified fromsplenocytes isolated from Balb/c mice by positive selection with αCD4mAb-coated microbeads (Miltenyi Biotec, Bergisch Gladbach, Germany).Thereafter, CD4⁺ T cells were stained with Cy-coupled αCD4 andPE-coupled αCD25 mAbs (BD Biosciences) and CD4⁺CD25⁺ T cells were sortedby FACS-sorting on a FAC-Star (BD Biosciences).

T Cell Cultures.

CD4⁺ T cells were obtained by incubation of splenocytes with αCD4mAb-coated microbeads and applied onto MiniMacs columns (MiltenyiBiotec). The average purity was 95%.

1×10⁶ CD4⁺ T cells isolated from spleen of DO11.10 tg mice werestimulated with 4×10⁶APC from Balb/c mice (i.e. total splenocytesirradiated 3000 Rad) and 0.6 μM OVA₃₂₃₋₃₃₉ peptide (OVA) (Primm, Milano,Italy). Three rounds of stimulation of 7 days each were performed. IL-2(BD Biosciences) was added starting from the second round of stimulationat 50 U/ml. Alternatively, 1×10⁶CD4⁺ T cells isolated from spleen ofBalb/c mice were stimulated with coated 10 μg/ml of αCD3 and soluble 1μg/ml of αCD28 mAbs (BD Biosciences). Cells were cultured in thepresence of medium alone or 100 nM rapamycin (Sigma, St Louis, Mo.).Three rounds of stimulation of 7 days each were performed. IL-2 (BDBiosciences) was added starting from the second round of stimulation at50 U/ml. In separate experiments, sorted CD4⁺CD25⁺ T cells isolated fromspleen of Balb/c mice were stimulated with coated 10 μg/ml of αCD3,soluble 1 μg/ml of αCD28 mAbs (BD Biosciences) and 1000 U/ml of IL-2.Cells were cultured in the presence of medium alone or 100 nM rapamycin(Sigma, St Louis, Mo.). 1000 U/ml of IL-2 was added at the beginning ofeach new stimulation.

FOXP3 Quantitative PCR.

Total RNA was extracted with Eurozol (Euroclone, Switzerland), and cDNAwas synthesized with High Capacity cDNA Archive Kit (Applied Biosystems,New Jersey, USA). Levels of FOXP3 mRNA was quantified using Assay onDemand real-time PCR kits (Applied Biosystems, New Jersey, USA) withTaqMan Universal PCR Master Mix (Applied Biosystems, New Jersey, USA).Levels of 18s rRNA was quantified as internal control by using TaqManPDAR Eukaryotic 18s Endogenus Controls (Applied Biosystems, assay ID:Mm00475156 ml). Samples were run in duplicate, and relative expressionof FOXP3 was determined by normalizing to 18s expression in each set ofsamples in order to calculate a fold-change in value.

Suppression Experiments.

CD4⁺ T cells isolated from naïve Balb/c mice or KJ1-26⁺ (αOVA-specificTCR) T cells isolated from DO11.10 tg mice were stained with CFSE(Molecular Probes) as described elsewhere (Lyons 1994) and cultured in96 well plates (2×10⁵/well) coated with 10 μg/ml αCD3 mAb (BDBiosciences) or irradiated splenocytes and OVA. T cells cultured for 3weeks in medium or rapamycin were added in 1:1 ratio (i.e. 10⁵:10⁵) tothe culture, and 5 days later the cells were collected and analyzed byFACS. The percentage of CFSE⁺ cells divided in the presence of culturedcells was compared to percentage of CFSE⁺ divided cells in the absenceof any added cells.

In the transwell experiments, CD4⁺ T cells isolated from naïve Balb/cmice were stained with CFSE (Molecular Probes) and cultured at thebottom of 48 transwell plates (5×10⁵/well) coated with 10 μg/ml αCD3 mAb(BD Biosciences). On top of the transwell were seeded T cells culturedfor 3 weeks in medium or rapamycin in 1:1 ratio, pre-activated with αCD3mAb for 6 hours. After 5 days of culture, cells from the bottomcompartment were collected and analyzed by FACS.

Cell Proliferation by CFSE Analysis.

The proportion of CFSE⁺ cells proliferating in vitro was calculated asdescribed elsewhere (Lyons 1994). Briefly, the number of cells (events)in a given cycle (division: n) was divided by 2 raised to power n, tocalculate the percentage of original precursor cells from which theyarose. The sum of original precursors from division 1 to 6 representsthe number of precursors cells which proliferated. The percent of CFSE⁺divided cells was calculated by [(# of precursors that proliferated₁₋₆/#of total precursors₀₋₆)×100].

Islet Transplant.

Diabetes was induced in Balb/c mice by intravenous injection ofstreptozotocin (Sigma, St. Louis, Mo.) at 170 mg/kg. A diagnosis ofdiabetes was made after two sequential glucose measurements higher than350 mg/dl. Hand picked pancreatic β-islets isolated from C57BL/6 weretransplanted under the kidney capsule of recipient Balb/c diabetic mice,as previously described (Davalli 1996).

Statistical Analysis.

All statistical analyses were performed using the Student t-test. KaplanMeier survival curves were compared by the log-rank test.

Example 1 Rapamycin does not Block Activation Induced Cell Death andProliferation of Murine CD4⁺ T Cells

To define the effect of rapamycin on T cells, naïve CD4⁺ T cells fromspleens of DO11.10 TCR tg mice were activated with APC+OVA in thepresence or absence of rapamycin and activation induced cell death(AICD) was monitored by binding of annexin V. In cells exposed torapamycin, neither increase nor reduction of apoptosis was observed uponin vitro activation, compared to control cells (FIG. 1A). In moredetail, DO11.10 tg CD4⁺ T cells were cultured with APC+OVA (medium) orAPC+OVA+rapamycin (rapamycin) and AICD was monitored by FACs after 24and 72 hours of culture. Percentage of PI⁺-annexinV⁺ cells is indicatedin each dot plot. These results confirm that rapamycin does not preventAICD in CD4⁺ T cells as already demonstrated in murine splenicmononuclear leukocytes activated with αCD3 mAb (Wells 1999), and inhuman peripheral blood mononuclear cells activated in primary mixedlymphocyte cultures (Koenen 2003).

To define the effects of a long-term exposure of T cells to rapamycin,naïve CD4⁺ T cells from DO11.10 TCR tg mice were activated in vitro withAPC+OVA for three consecutive weeks in the presence or absence ofrapamycin. Fold expansion of T cells was determined after each round ofstimulation. As shown in FIG. 1B, fold expansion of DO11.10 tg CD4⁺ Tcells 1, 2, and 3 weeks after culture in the presence of APC+OVA(medium, white bars) or APC+OVA+rapamycin (rapamycin, dotted bars) wasevaluated by direct cell counts. T cells activated in the presence ofrapamycin had a delayed kinetic of proliferation compared to controlcells. However, at the end of the third week of culture the same numberof T cells was recovered in control- and rapamycin-cultures (FIG. 1B).Rapamycin binds to FKBP12 and the formed complex inhibits the functionof mTOR, which is involved in a broad range of physiological processeslinked to the control of cell-cycle. Indeed, rapamycin is widelyconsidered as an inhibitor of T cell cycle by arresting T cells in G₁phase (Dumont 1990, Chung 1992, Morice 1993, Nourse 1994, Kato 1994).Based on this mode of action, rapamycin is used as an immunosuppressiveagent for the treatment of transplant rejection. However, patients whoreceived rapamycin did not reveal higher susceptibility to infections,as expected by general immunosuppression (Saunders 2001). Furthermore,it has been demonstrated that rapamycin has some effects in blockingCD4⁺ T cell cycle entry, but the majority of the cells, once enter thecell cycle, are perfectly capable of dividing (Terada 1993, Terada 1995,Vu 2004). In line with these observations, our results demonstrate thatrapamycin does not block CD4⁺ T cells expansion.

After one, two (data not shown), or three rounds of stimulation (FIG.1C), CD4⁺ T cells activated in the presence of rapamycin andre-stimulated with APC+OVA in the absence of rapamycin, retained theirability to proliferate, although the overall number of cell divisionswas slightly reduced. In more detail in relation to FIG. 1C, after 3rounds of stimulation with APC+OVA (medium) or APC+OVA+rapamycin(rapamycin), DO11.10 tg CD4⁺ T cells were stained with CFSE andre-stimulated with APC+OVA in the absence of the compound and ofexogenous IL-2. CFSE dilution was monitored 5 days after activation.

These data indicate that exposure to rapamycin does not induce anergy inCD4⁺ T cells. These results are in line with those reported in vitro byKoenen et al. (2003) and in vivo by Ghobrial et al. (1996), but are incontrast with the findings of Powell and colleagues who showed that aTh1 cell clone responding to APC+Ag become anergic when treated withrapamycin (Powell 1999). One possible explanation for the observeddifferences might be that, in the aforementioned study a murine CD4⁺ Tcell clone stimulated with APC+Ag and rapamycin overnight was tested,whereas in our experimental model we used a polyclonal T cell populationactivated in an Ag-specific way for three times in the presence ofrapamycin.

Although T cells repetitively activated in vitro for three weeks in thepresence of rapamycin proliferated similarly to control cells,rapamycin-exposed CD4⁺ T cells were smaller and displayed a moreround-like shape than control cells (FIG. 1D). After 3 rounds ofstimulation with APC+OVA (medium) or APC+OVA+rapamycin (rapamycin),DO11.10 tg CD4⁺ T cells were left resting for one additional week withno further stimulation in the presence of IL-2 (50 U/ml). At the end ofthe seven days cell size was analyzed by FACS by plotting FSC vs SSCparameters. Small (continuous line) and big (dotted line) cells arecircled. Naïve CD4⁺ T cells from a DO11.10 tg mouse were used ascontrol.

Studies performed in model genetic organisms suggest that cell divisionand cell growth are normally coordinated yet separable processes andthat cells progress through the cell cycle only when sufficient mass,size, and biosynthesis have been reached (reviewed in Schmelzle 2000).On the contrary, Fingar and colleagues demonstrated that cell growth andcell cycle progression are separable processes in mammalian cells andthat growth to appropriate cell size requires mTOR-dependent signals. Inthis study it was demonstrated that inhibition of mTOR is the mechanismby which rapamycin reduces cell size in rat fibroblasts and humanosteosarcoma cell lines (Fingar 2002). In line with these findings, ourdata provide evidence that rapamycin blocks CD4⁺ T cells growth whileallows their proliferation.

Example 2 Rapamycin Expands CD4⁺CD25⁺FOXP3⁺ Tr Cells with SuppressiveAbility In Vitro

After 3 rounds of stimulation with APC+OVA (medium) or APC+OVA+rapamycin(rapamycin), DO11.10 tg CD4⁺ T cells were left resting for one week withno further stimulation in the presence of IL-2 (50 U/ml). After sevendays cells were analyzed by FACS. Cells were gated on CD4⁺CD25⁺ cellsand numbers represent percentages of the three different CD25⁺ subset(i.e. bright, dim, and low). Naïve CD4⁺ T cells from a DO11.10 tg mousewere used as control.

Content of CD25^(bright) T cells in medium- and rapamycin-cultures ineach of the 6 experiments is presented. Star indicates statisticalsignificance (*0.001<p≦0.05).

T cells activated in the presence of rapamycin were highly enriched inCD4⁺CD25^(bright) T cells, which represent the Tr subset among theCD4⁺CD25⁺ T cell population (FIGS. 2A and B) (Levings 2002, Belghith2003).

1×10⁶ DO11.10 tg CD4⁺ T cells (containing 70.000 CD4⁺CD25^(bright) Tcells) were cultured with APC+OVA (medium, white bar) orAPC+OVA+rapamycin (dotted bar, rapamycin). After 3 rounds ofstimulation, the total number of CD4+CD25^(bright) T cells wasdetermined by FACS. Accordingly, the total number of CD4+CD25^(bright) Tcells recovered after three weeks of culture and repetitiveAg-stimulation in the presence of rapamycin was markedly superior tothat of control cultures (FIG. 2C).

Interestingly, rapamycin-exposed CD4⁺ T cells were able to suppressproliferation of syngeneic naïve CD4⁺ T cells activated in vitro withAPC+OVA (FIG. 3A, left panel). These data clearly indicate that,although cells exposed to rapamycin are not an homogeneous populationand contain around 60% of CD4⁺CD25^(bright) Tr cells (FIG. 2A), theydisplay a strong suppressive capacity in vitro.

It has been demonstrated that rapamycin profoundly affects the phenotypeand function of dendritic cells by reducing their Ag uptake capacity,thereby favoring the differentiation of tolerogenic APC (Hackstein2002). Thus, the presence of Tr cells in rapamycin-exposed T cellcultures could be due to an indirect effect of rapamycin on APC, whichbecome tolerogenic and induce a Tr cell population, rather than a directeffect on the T cells. To test this hypothesis, we investigated theeffects of long-term exposure of T cells to rapamycin in an “APC-free”system. Naïve CD4⁺ T cells from spleens of Balb/c mice were repetitivelyactivated in vitro with αCD3 and αCD28 mAbs for three weeks in thepresence or absence of rapamycin. As demonstrated for T cells activatedwith APC+OVA, T cells activated with αCD3 and αCD28 mAbs in the absenceof APC, proliferated, did not become anergic, were smaller than controlcells (data not shown), and suppressed proliferation of syngeneic naiveCD4⁺ T cells in vitro (FIG. 3A, right panel). In more detail, NaïveKJ1-26⁺CD4⁺ tg T cells isolated from spleens of DO11.10 tg mice, werestained with CFSE and were activated with APC alone or APC+OVA. DO11.10CD4⁺ T cells activated for 3 weeks with APC+OVA (medium-cells) orAPC+OVA+rapamycin (rapamycin-cells) were added in equal number to naïveCFSE⁺ cells (10⁵:10⁵) (left panel). Alternatively, naïve CD4⁺ cellsisolated from spleens of Balb/c mice were labeled with CFSE and culturedalone (unstimulated) or with αCD3 mAb. Balb/c CD4⁺ T cells activated for3 weeks with αCD3+αCD28 mAbs (medium-cells) or αCD3+αCD28 mAbs+rapamycin(rapamycin-cells) were added in equal number to naïve CFSE⁺ cells(10⁵:10⁵) (right panel). After 5 days of culture, cell division wasmonitored by levels of CFSE dilution. Histograms show the FACs profileof CD4⁺CFSE⁺ T cells. Number of events in each cell division (n) areindicated on top of each peak. The amount of CD4⁺CFSE⁺ cellsproliferating in the absence or presence of cultured T cells wascalculated as described in the Methods and percentages of undividedcells in each culture condition is indicated. Percentages of suppressionin comparison to proliferation of naïve control cells is indicated.

These data demonstrate that rapamycin induces Tr cells by directlyacting on CD4⁺ T cells.

The suppressive ability of rapamycin-exposed T cells was also tested ina transwell system in which responder and suppressor cells were keptseparate. Using the same cells described in FIG. 3A (right panel), theexperiment was performed in a transwell system in which responder naïveCD4⁺ T cells were activated with αCD3 mAb at the bottom of the transwellwhile medium- or rapamycin-cells were pre-activated with αCD3 mAb for 6hours and then added on top of the transwell (right panel). Dataobtained in the transwell system were compared to data obtained in theco-colture system (left panel). Rapamycin-exposed T cells were able tosuppress proliferation of syngeneic naïve CD4⁺ T cells only in aco-colture system (FIG. 3A) indicating that their suppressive capacitywas strictly dependent on cell-cell contact.

The presence of CD4⁺CD25⁺ Tr cells with suppressive activity inrapamycin-exposed T cell cultures may be due to either a de-novoinduction of CD25⁺ Tr cells from CD25⁻ T cells or to a selectiveexpansion of the naturally occurring CD4⁺CD25⁺FOXP3⁺ Tr cell subsetalready present in limited amounts at the beginning of the culture (i.e.the ˜10% of CD4⁺CD25^(bright) T cells usually found in a naive spleen).To address this question, CD4⁺ T cells depleted of the CD25⁺ Tr cellswere cultured for three weeks in the presence or absence of rapamycin.In contrast to CD4⁺ T cells (FIG. 3A), CD4⁺CD25⁻ T cells activated inthe presence of rapamycin gave rise to a population of T cells thatfailed to suppress cell proliferation in vitro (FIG. 4A). Accordingly,FOXP3 expression was enhanced only in CD4⁺ T cells exposed to rapamycinbut not in CD4⁺CD25⁻ rapamycin-treated T cells (FIG. 4B). In moredetail, the same experiment described in FIG. 3A (left panel) with cellsfrom DO11.10 tg mice was performed using CD4⁺CD25⁻ T cells cultured for3 weeks with APC+OVA (medium-cells) or APC+OVA+rapamycin(rapamycin-cells). The cultured cells were added in equal number tonaïve KJ1-26⁺CFSE⁺ cells (10⁵:10⁵) and proliferation was monitored byCFSE dilution. FACS profile of the cells used before culture (startingpopulation) is shown on top in FIG. 4A. Relative levels of mRNA FOXP3were determined by real time quantitative RT-PCR in CD4⁺ (left panel) orCD4⁺CD25⁻ (right panel) T cells repetitively activated in vitro with orwithout rapamycin. The amounts of FOXP3 mRNA are expressed as relativeto that in splenocytes depleted of CD4⁺CD25⁺ T cells (which was given anarbitrary value of 1). Relative levels of mRNA FOXP3 in the cells beforeculture (start) are also indicated in FIG. 4B.

These data indicate that depletion of CD4⁺CD25⁺ T cells from thestarting cell population does not allow the rapamycin-mediated expansionof Tr cells. However, one can not exclude the possibility that CD4⁺CD25⁺Tr cells are indispensable in the culture for the generation ofrapamycin-mediated induction of Tr cells from a CD4⁺CD25⁻ T cellpopulation. To address this point, highly purified sorted CD4⁺CD25⁺ Tcells (FIG. 5A) were activated with αCD3 and αCD28 mAbs and cultured forthree weeks in the presence or absence of rapamycin. Thus, CD4⁺CD25⁺ Tcells isolated from spleens of Balb/c mice were sorted by FACS and theFACS profile of sorted CD4⁺CD25⁺ T cells is shown in FIG. 5A. Sortedcells were 93% CD4⁺CD25⁺ among which 46% were CD4⁺CD25^(bright) T cells.High doses of IL-2 (i.e. 1000 U/ml) in the cultures were necessary toexpand sorted CD4⁺CD25⁺ T cells, which otherwise were anergic (data notshown).

Fold expansion of Balb/c CD4⁺CD25⁺ T cells 1, 2, and 3 weeks afterculture in the presence of αCD3+αCD28+1000 U/ml IL-2 (medium, whitebars) or αCD3+αCD28+1000 U/ml IL-2+rapamycin (rapamycin, dotted bars)was evaluated by direct cell counts. After 3 rounds of stimulation withαCD3+αCD28+1000 U/ml IL-2 (medium) or αCD3+αCD28+1000 U/mlIL-2+rapamycin (rapamycin), Balb/c CD4⁺CD25⁺ T cells were left restingfor one week with no further stimulation in the presence of low doseIL-2 (50 U/ml). After seven days, cells were analyzed by FACS. Cellswere gated on CD4⁺CD25⁺ cells and numbers represent percentages of thethree different CD25⁺ subset (i.e. bright, dim, and low). The resultsare shown in FIGS. 5B and C. T cells activated in the presence ofrapamycin had a delayed kinetic of proliferation compared to controlcells. However, starting from the third week of culture, CD4⁺CD25⁺ Tcells activated in the presence of rapamycin greatly expanded whilecontrol T cells showed reduced proliferation likely due to exhaustionafter repeated TCR stimulation in the presence of high doses of IL-2(FIG. 5B). CD4⁺CD25⁺ T cells activated for three weeks in the presenceof rapamycin contained a higher percentage of CD4⁺CD25^(bright) T cellscompared to control cells (FIG. 5C).

The same experiment described in FIG. 3A (right panel) with cells fromBalb/c mice was performed using CD4⁺CD25⁺ T cells cultured for 3 weekswith αCD3+αCD28+1000 U/ml IL-2 (medium-cells) or αCD3+αCD28+1000 U/mlIL-2+rapamycin (rapamycin-cells). The cultured cells were added in equalnumber to naïve CD4⁺ T cells isolated from Balb/c mice (10⁵:10⁵) andproliferation was monitored by CFSE dilution.

Relative levels of mRNA FOXP3 were determined by real time quantitativeRT-PCR in Balb/c CD4⁺CD25⁺ T cells repetitively activated in vitro withor without rapamycin. The amounts of FOXP3 mRNA are expressed asrelative to that in splenocytes depleted of CD4⁺CD25⁺ T cells (which wasgiven an arbitrary value of 1). Relative levels of mRNA FOXP3 in thecells before culture (start) are also indicated.

Accordingly, only rapamycin-exposed CD4⁺CD25⁺ T cells suppressedproliferation of syngeneic CD4⁺ T cells in vitro (FIG. 6A) and preservedFOXP3 expression (FIG. 6B). Surprisingly, CD4⁺CD25⁺ T cells expanded inthe absence of rapamycin lost their suppressive function in vitro (FIG.6A). While it has been previously shown that CD4⁺CD25⁺ T cells can beexpanded in vitro for 1 week with αCD3 and αCD28 mAbs and high doses ofIL-2 without loosing their suppressive function (Taylor 2002), it ispossible that repeated activation and culture of CD4⁺CD25⁺ T cells inmedium and high doses of IL-2 results in an overgrowth of activatedCD4⁺CD25⁺ effector T cells rather than an expansion of CD4⁺CD25⁺ Trcells.

Diabetic Balb/c mice were transplanted under the kidney capsule withpancreatic β-islets purified from C57BL/6 mice. Mice were not treated(control n=4), or injected the day before the transplant with 5×10⁶ CD4⁺T cells isolated from Balb/c mice and activated for 3 weeks in thepresence of rapamycin (rapamycin-cells, n=6). Graft survival wasmonitored by glycemia levels. A graft was considered rejected whenglycemia was higher than 250 mg/dl. Kaplan Meier survival curves werecompared by the log-rank test. The results are shown in FIG. 7

Overall these data demonstrate that rapamycin selectively expands thenaturally occurring CD4⁺CD25⁺FOXP3⁺ Tr cells normally present in thenaïve splenic CD4⁺ T cell compartment and that CD4⁺CD25⁺ Tr cellsrepetitively activated for three weeks in the presence of high doses ofIL-2 preserve their phenotype and in vitro suppressive function onlywhen cultured in the presence of rapamycin.

Materials and Methods for Example 3 Mice.

NOD female mice were purchased from Charles River Laboratories (Calco,Italy). All mice were kept under specific pathogen free conditions.

Murine T Cell Cultures.

CD4⁺ T cells were obtained by incubation of splenocytes frompre-diabetic or diabetic NOD mice with αCD4 mAb-coated microbeads andapplied onto MiniMacs columns (Miltenyi Biotec). The average purity was95%. 1×10⁶ CD4⁺ T cells isolated from spleen of NOD mice were stimulatedwith coated 10 μg/ml of αCD3 and soluble 1 μg/ml of αCD28 mAbs (BDBiosciences). Cells were cultured in the presence of medium alone or 100nM rapamycin (Sigma, St Louis, Mo.). Three rounds of stimulation of 7days each were performed. IL-2 (BD Biosciences) was added starting fromthe second round of stimulation at 100 U/ml.

Suppression Experiments.

CD4⁺ T cells isolated from pre-diabetic NOD mice were stained with CFSE(Molecular Probes) as described elsewhere (Lyons 1994) and cultured in96 well plates (2×10⁵/well) coated with 10 μg/ml αCD3 mAb (BDBiosciences). T cells cultured for 3 weeks in medium or rapamycin wereadded in 1:1 ratio (i.e. 10⁵:10⁵) to the culture, and 5 days later thecells were collected and analyzed by FACS. The percentage of CFSE⁺ cellsdivided in the presence of cultured cells was compared to percentage ofCFSE⁺ divided cells in the absence of any added cells.

Example 3 Rapamycin Expands CD4⁺CD25⁺ Tr Cells from Normal and DiabeticNOD Mice

In this Example, we attempted to generate ex vivo Tr cells from nonobese diabetic (NOD) mice. Spontaneously autoimmune diabetes in NOD micemainly results from quantitative and qualitative changes inautoaggressive T effector cells. Older mice indeed harbor diabetogenic Tcells that are progressively less prone to Tr cells-mediated inhibition(You et al. Diabetes, 2005). We tested whether rapamycin could expandfunctional Tr cells from NOD mice and whether these expanded T cellshave a regulatory function. CD4⁺ T cells were isolated from the spleenof pre-diabetic 11 week old NOD mice and were activated in vitro withanti-CD3 and CD28 mAbs in the presence of medium or rapamycin. Afterthree round of stimulations, T cells cultured in the presence ofrapamycin were highly enriched in CD4⁺CD62L⁺ and CD45RB^(low) cells, andexpressed higher levels of CD25 compared to medium culture conditions(data not shown). Interestingly, rapamycin-expanded NOD CD4⁺ T cells notonly were enriched in cells expressing regulatory markers, but were alsosuppressive in vitro (FIG. 8).

In more detail in relation to FIG. 8, T cells isolated from NOD mice andexpanded ex vivo in the presence of rapamycin are suppressive in vitro.Naïve CD4⁺ T cells isolated from spleens of pre-diabetic NOD mice werestained with CFSE and were cultured alone (unstimulated) or withanti-CD3 mAb. NOD CD4⁺ T cells activated for 3 weeks in the presence ofmedium or rapamycin, and were added in equal number to naïve CFSE⁺ cells(10⁵:10⁵). After 5 days of culture, cell division was monitored bylevels of CFSE dilution. Histograms show the FACS profile of naïveCD4⁺CFSE⁺ T cells. Percentage of divided cells is shown on top of eachhistogram. Percentage of suppression in comparison to proliferation ofnaïve control cells in the presence of medium-cells is indicated on theleft. One representative experiment out of 2 is presented.

To test the ability of the ex vivo expanded NOD T cells to suppressautoimmune diabetes in vivo, 5 million of rapamycin-expanded T cellswere injected in pre-diabetic NOD mice of 10 weeks of age and diabetesdevelopment was monitored throughout 30 weeks. At 40 weeks of age, allcontrol non-injected NOD mice developed diabetes (n=6) and the adoptivetransfer of medium-expanded T cells did not prevent diabetes.Interestingly, transfer of rapamycin-expanded T cells prevented diabetesdevelopment to some extent (60% diabetes incidence n=6) (FIG. 9). Thesepreliminary data suggest that rapamycin can expand Tr cells ex vivo frompre-diabetic NOD mice which suppress cell proliferation in vitro andthat these cells could prevent autoimmunity in vivo.

In more detail in relation to FIG. 9, Rapamycin-expanded NOD cellsreduce diabetes development in vivo. Pre-diabetic NOD mice 10 week oldwere not treated (◯ control n=6), or injected with 5×10⁶ CD4⁺ T cellsisolated from NOD mice and cultured for 3 weeks with medium (♦ n=6) orrapamycin (▪ n=5). Diabetes incidence was monitored by glycemia levelsup to 40 weeks of age.

A cellular-therapy-based approach to treat type 1 diabetes is likely torequire the use of autologous T cells isolated from diabetic subjects.It is therefore crucial to define whether Tr cells can be expanded exvivo from already diabetic individuals. To this attempt, we definedwhether rapamycin can expand ex vivo Tr cells from overtly diabetic NODmice. CD4⁺ T cells were isolated from the spleen of NOD mice with overtdiabetes and were expanded ex vivo for 3 weeks with anti-CD3 and CD28mAbs in the presence or absence of rapamycin. At the end of the thirdweek of stimulation, the expanded T cells were tested for their abilityto suppress syngeneic CD4⁺ T cells in vitro. T cells expanded withrapamycin efficiently suppressed cell proliferation (FIG. 10). Thesedata indicate that rapamycin can efficiently expands Tr cells ex vivoalso from a cell pool, which includes diabetogenic T cells.

In more detail in relation to FIG. 10, T cells isolated from diabeticNOD mice and expanded in the presence of rapamycin are suppressive invitro. Naïve CD4⁺ T cells isolated from spleens of pre-diabetic NOD micewere stained with CFSE and were cultured alone (unstimulated) or withanti-CD3 mAb. CD4⁺ T cells isolated from diabetic NOD and activated for3 weeks in the presence of medium, or rapamycin, were added in equalnumber to naïve CFSE⁺ cells (10⁵:10⁵). After 5 days of culture, celldivision was monitored by levels of CFSE dilution. Histograms show theFACS profile of CD4⁺CFSE⁺ T cells. Percentage of divided cells is shownon top of each histogram. Percentage of suppression in comparison toproliferation of naïve control cells in the presence of medium-cells isindicated on the left.

Overall these new data demonstrate that rapamycin selectively expandsthe naturally occurring CD4⁺CD25⁺FOXP3⁺ Tr cells present in the spleenof normal and diabetic NOD mice.

Materials and Methods for Examples 4-8 Cell Purification.

Peripheral blood mononuclear cells were separated by density-gradientcentrifugation over Lymphoprep (Amersham Biosciences). CD4⁺ T cells werepurified by negative selection using a CD4⁺ T cell enrichment kit(Miltenyi Biotec, Bergisch Gladbach, Germany).

Flow Cytometry.

Cells were stained with the indicated surface Abs (all from BDBiosciences, Mountain View, Calif.), and were analyzed with a FACScanflow cytometer equipped with CellQuest software (BD Biosciences).Intra-cytoplasmic staining for h-FOXP3 was performed using theanti-FOXP3 APC staining Kit (eBioscience) following the productinstruction.

T Cell Cultures.

CD4⁺ T cells isolated from PBMCs of healthy subjects or T1D patientswere activated with plate bound anti-CD3 (10 μg/ml) and soluble ofanti-CD28 (1 μg/ml) mAbs (BD Biosciences). Cells were cultured in thepresence of medium α-vivo 10) alone or with 100 nM rapamycin (Sigma, StLouis, Mo.). Three round of stimulations of 7 days each were performed.IL-2 (BD Biosciences) was added starting from the second round ofstimulation at 100 U/ml.

Suppression Experiments.

Purified CD4⁺ T cells or CD4⁻ PBMCs from healthy subjects or T1Dpatients were stained with CFSE (Molecular Probes, Eugene, Oreg.) asdescribed elsewhere {Lyons, 1994#22} and cultured in 96 well plates(2×10⁵/well) pre-coated with anti-CD3 (10 μg/ml) and with soluble ofanti-CD28 (1 μg/ml) mAbs (BD Biosciences). T cells cultured for 3 weeksin medium or rapamycin were first stained with SNARF (Molecular Probes)following the same protocol as for CFSE staining, and subsequently wereadded in 1:1 ratio (i.e. 10⁵:10⁵) to the culture. Seven days later thecells were collected and analyzed by FACS. The percentage of CFSE⁺ cellsdivided in the presence of cultured cells was compared to percentage ofCFSE⁺ divided cells in the absence of any added cells.

The proportion of CFSE⁺ (FL-1) responding T cells proliferating in vitrowas calculated by gating on lymphocytes and alive cells (TOPRO⁻ FL-4,Molecular Probe) and by excluding SNARF⁺ (FL-2) cells. The number ofgated cells (events) in a given cycle (division: n) was divided by 2raised to power n, to calculate the percentage of original precursorcells from which they arose. The sum of original precursors fromdivision 1 to 6 represents the number of precursors cells whichproliferated. The percent of CFSE⁺ divided cells was calculated by [(#of precursors that proliferated₁₋₆/# of total precursors₀₋₆)×100]{Lyons, 1994#22}.

Example 4 Rapamycin Strongly Reduces TCR-Mediated Proliferation of CD4⁺T Cells and does not Induce T Cell Anergy

CD4⁺ T cells were stained with CFSE either at the beginning of theculture (1^(st) week), or at the end of one (2^(nd) week), or three(4^(th) week) round of stimulations. CFSE⁺CD4⁺ T cells were activated invitro in the presence of anti-CD3+anti-CD 28 mAbs in the presence orabsence of 100 nM rapamycin. CFSE dilution was monitored 7 days afteractivation. One representative experiment out of 6 is presented in FIG.11A.

In FIG. 11B the number of CD4⁺ T cells present at the beginning (start)and at the end (4^(th) week) of the culture in the presence or absenceof rapamycin is shown. Each line represents one experiment (n=14).

CD4⁺ T cells were stained with CFSE and activated withanti-CD3+anti-CD28 mAbs in the presence or absence of rapamycin. Afterseven days, cells were stained with propidium iodide (PI) and wereanalyzed by FACS. Numbers represent percentages of divided dead cells(CFSE^(diluted)-PI⁺), undivided dead cells (CFSE^(undiluted)-PI⁺),undivided alive cells (CFSE^(undiluted)-PI⁻), and divided alive cells(CFSE^(diluted)-PI). In FIG. 11C one representative experiment out of 5is presented.

After 3 round of stimulations with anti-CD3+anti-CD28 mAbs (T medium) oranti-CD3+anti-CD28 mAbs+rapamycin (T rapamycin), CD4⁺ T cells werestained with CFSE and re-stimulated with anti-CD3+anti-CD28 mAbs in theabsence of the compound and of exogenous IL-2. CFSE dilution wasmonitored 7 days after activation. Numbers indicate the percentage ofdividing cells. One representative experiment out of 3 is presented inFIG. 11D.

Example 5 Rapamycin-Expanded CD4⁺ T Cells Express Regulatory Markers andSuppress Proliferation of Syngeneic and Allogeneic CD4+ and CD8⁺ T Cells

Expression of CD25 and FOXP3 by freshly isolated CD4⁺ T cells beforeculture was tested by FACS. The results are shown in FIG. 12A.

After 3 rounds of stimulation with anti-CD3+anti-CD28 mAbs (T medium) oror anti-CD3+anti-CD28 mAbs+rapamycin (T rapamycin), CD4⁺ T cells wereleft resting for one week with no further stimulation in the presence ofIL-2 (10 U/ml). After seven days cells were analyzed by FACS. Onerepresentative experiment out of 8 is presented in FIG. 12B.

Purified CD4⁺ T cells isolated from healthy subject, were stained withCFSE and were activated with anti-CD3+anti-CD28 mAbs (responder CD4⁺ Tcells, FIG. 12C left panel). Alternatively, CD4⁻ cells isolated fromhealthy subject, were stained with CFSE and were activated withanti-CD3+anti-CD28 mAbs. Proliferation of CD8⁺ T cells was followed uponstaining with anti-CD8 mAb at the moment of FACS analysis (responderCD8⁺ T cells, FIG. 12C right panel). CD4⁺ T cells isolated from the samesubject used as responder (self) or from an unrelated donor (allo) andactivated for 3 weeks with anti-CD3+anti-CD28 mAbs (T medium) oranti-CD3+anti-CD28 mAbs+rapamycin (T rapamycin) were added in equalnumber to responder CFSE⁺ cells (10⁵:10⁵). After 7 days of culture, celldivision was monitored by levels of CFSE dilution. Histograms show theFACS profile of CFSE⁺ T cells. The amount of CFSE⁺ cells proliferatingin the absence or presence of cultured T cells was calculated andpercentages of divided cells in each culture condition is indicated.Percentages of suppression in comparison to proliferation of respondercells is indicated. One representative experiment is presented in FIG.12C.

Percentage of suppression in each performed experiments is presented inFIG. 12D. Each dot represents one experiment. The line representsaverage of suppression. There was no statistically significantdifferences between suppression versus responder self-CD4⁺ T cells andversus allo-CD4⁺ T cells.

Example 6 Rapamycin Selectively Blocks TCR-Mediated Proliferation ofCD4⁺CD25⁻ T Cells but not of CD4⁺CD25⁺ Tr Cells

CD4⁺CD25⁻ and CD4⁺CD25^(bright) T cells were FACS sorted. Subsequently,sorted CD4⁺CD25⁻ T cells were stained with CSFE and sorted CD4⁺CD25⁺ Tcells were added back to the same amount present in unsorted CD4⁺ Tcells (5%) (FIG. 13, left panel). Alternatively, sorted CD4⁺CD25⁺ Tcells were stained with CSFE and sorted CD4⁺CD25⁻ T cells were addedback to the same amount present in unsorted CD4⁺ T cells (95%) (rightpanel of FIG. 13). The two distinct CFSE stained cell populations wereactivated with anti-CD3+anti-CD28 mAbs+IL-2 in the presence or absenceof 100 nM rapamycin. CFSE dilution was monitored 7 days afteractivation. Numbers indicate the percentage of CFSE⁺ dividing cells. Onerepresentative experiment out of 2 is presented in FIG. 13.

Example 7 T Cells of Normal Donors and T1D Patients Express SimilarLevels of FOXP3

FOXP3 expression was tested by FACS on purified CD4⁺ T cells isolatedfrom normal donors (ND) and type 1 diabetic patients (T1D). Onerepresentative histogram is shown in FIG. 14. Percentage of CD4⁺FOXP3⁺cells in each T1D patients tested (n=5) and in ND is also shown. Eachdot represents one donor. The line represents average of CD4⁺FOXP3⁺ Tcells. There was no statistically significant differences betweenFOXP3-expressing cells in ND versus T1D subjects. No difference in FOXP3expression between ND and T1D patients was observed when the analysiswas performed on CD4⁺CD25^(bright) T cells.

Example 8 Rapamycin-Expanded T Cells from T1D Patients SuppressProliferation of CD4⁺ and CD8⁺ T Cells

CD4⁺ T cells isolated from normal donor, were stained with CFSE and wereactivated with anti-CD3+anti-CD28 mAbs (responder CD4⁺ T cells, FIG. 15left panel). Alternatively, CD4⁻ cells isolated from T1D patient (middlepanel) or normal donor (right panel), were stained with CFSE and wereactivated with anti-CD3+anti-CD28 mAbs. Proliferation of CD8⁺ T cellswas followed upon staining with anti-CD8 mAb at the moment of FACSanalysis (responder CD8⁺ T cells). CD4⁺ T cells isolated from the samesubject used as responder (self) or from an unrelated donor (allo) andactivated for 3 weeks with anti-CD3+anti-CD28 mAbs (T medium) oranti-CD3+anti-CD28 mAbs+rapamycin (T rapamycin) were added in equalnumber to responder CFSE⁺ cells (10⁵:10⁵). After 7 days of culture, celldivision was monitored by levels of CFSE dilution. Histograms in FIG. 15show the FACS profile of CFSE⁺ T cells. The amount of CFSE⁺ cellsproliferating in the absence or presence of cultured T cells wascalculated as described in the above methods and percentages of dividedcells in each culture condition is indicated. Percentages of suppressionin comparison to proliferation of responder cells is indicated.

Percentage of suppression in each performed experiments is presented.Each dot represents one experiment. The line represents average ofsuppression.

All publications mentioned in the above specification are hereinincorporated by reference. Various modifications and variations of thedescribed methods and system of the invention will be apparent to thoseskilled in the art without departing from the scope and spirit of theinvention. Although the invention has been described in connection withspecific preferred embodiments, it should be understood that theinvention as claimed should not be unduly limited to such specificembodiments. Indeed, various modifications of the described modes forcarrying out the invention which are apparent to those skilled incellular and/or molecular biology or related fields are intended to bewithin the scope of the following claims.

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1-25. (canceled)
 26. A CD4⁺CD25⁺ Tr cell or a population of T cellsproducible by a method selected from the group consisting of: (i) an invitro method for producing a CD4⁺CD25⁺ T regulatory (Tr) cell comprisingincubating a T cell or a population of T cells obtainable from a humanor animal with rapamycin or a derivative thereof; (ii) an in vitromethod for expanding or culturing a population of CD4⁺CD25⁺ Tr cells ina population of T cells comprising incubating a population of T cellsobtainable from a human or animal with rapamycin or a derivativethereof; and (iii) an in vitro method for selectively eliminating orreducing CD4⁺CD25⁻ T cells in a population of T cells comprisingincubating a population of T cells obtainable from a human or animalwith rapamycin or a derivative thereof.
 27. A CD4⁺CD25⁺ Tr cell or apopulation of T cells according to claim 26 wherein the population of Tcells used in the in vitro method comprises CD4⁺CD25⁺ Tr cells andCD4⁺CD25⁻ T cells.
 28. A CD4⁺CD25⁺ Tr cell or a population of T cellsaccording to claim 26 wherein the T cell or population of T cellsobtainable from a human or animal used in the in vitro method isobtainable from a sample comprising T cells from a human or animal. 29.A CD4⁺CD25⁺ Tr cell or a population of T cells according to claim 28wherein the sample used in the in vitro method is a blood sample or asample from a lymphoid organ.
 30. A CD4⁺CD25⁺ Tr cell or a population ofT cells according to claim 28 wherein the T cell or population of Tcells used in the in vitro method are CD4⁺ T cells isolated from thehuman or animal sample.
 31. A CD4⁺CD25⁺ Tr cell or a population of Tcells according to claim 28 wherein the T cell or population of T cellsobtainable from a human or animal used in the in vitro method arepurified prior to incubation with rapamycin.
 32. A CD4⁺CD25⁺ Tr cell ora population of T cells according to claim 26 wherein the T cell orpopulation of T cells obtainable from a human or animal used in the invitro method are activated.
 33. A CD4⁺CD25⁺ Tr cell or a population of Tcells according to claim 26 wherein said in vitro method furthercomprises incubating the T cell or population of T cells obtainable froma human or animal in the presence of a cytokine.
 34. A CD4⁺CD25⁺ Tr cellor a population of T cells according to claim 33 wherein the cytokineused in the in vitro method is IL-2.
 35. A CD4⁺CD25⁺ Tr cell or apopulation of T cells according to claim 26 wherein the in vitro methodfurther comprises incubating the T cell or population of T cellsobtainable from a human or animal in the presence of an antigen.
 36. ACD4⁺CD25⁺ Tr cell or a population of T cells according to claim 35wherein the antigen used in the in vitro method is an allergen,allo-antigen, self-antigen, food antigen, and microbial antigen.
 37. ACD4⁺CD25⁺ Tr cell or a population of T cells according to claim 26 forcellular therapy.
 38. A CD4⁺CD25⁺ Tr cell or cell population accordingto claim 24 for the modulation of a cell-mediated immune response.
 39. ACD4⁺CD25⁺ Tr cell or cell population according to claim 38 where thecell mediated immune response is a T cell- or an antibody-mediatedimmune response.
 40. A CD4⁺CD25⁺ Tr cell or cell population according toclaim 38 for the preventive or therapeutic treatment of allogenic solidorgan rejection and graft versus host disease.
 41. A pharmaceuticalcomposition comprising the CD4⁺CD25⁺ Tr cell or cell populationaccording to claim 26 and a pharmaceutically acceptable carrier,excipient or diluent.